British-Australian academic Kylie Moore-Gilbert has not been reported among the 85,000 prisoners temporarily released from Iranian jails out of fear coronavirus could sweep through the country’s overcrowded prisons.

As the Iranian government struggling to contain an exponential rise in Covid-19 cases – currently the country has 16,000 confirmed cases and nearly 1,000 deaths – a doctor on state-run TV warned more than three million people could die across the country if isolation measures aren’t strictly adhered to.

There are growing concerns for prisoners held in Iran’s overcrowded jails, where healthcare is poor and many prisoners have already compromised health. The government says it has released half of the country’s “security” prisoners on furlough to arrest any potential Covid-19 spread, but nothing has been heard publicly on Moore-Gilbert’s case.

Lines of communication to Moore-Gilbert through other prisoners have been cut in recent days and weeks with the transfer and furloughing of thousands of prisoners.

Moore-Gilbert has been publicly silent for months, since a series of smuggled letters were published detailing the privations of her imprisonment, including months isolated in solitary confinement, and a shortage of food, medicine, and money to buy personal items.

Moore-Gilbert has been held in the isolated ward 2A of Evin, run by the Revolutionary Guards, and it is known she has previously gone on several long-running hunger strikes.

“Australia’s Department of Foreign Affairs and Trade is urging all Australians to come home so it should absolutely prioritise the return of vulnerable Australian like Kylie Moore-Gilbert who are arbitrarily detained abroad,” said Elaine Pearson, Australia director for Human Rights Watch.

“Governments are closing their borders, flights are becoming more limited and it will only get worse. Prison is no place to be when there is a pandemic. There are grave risks to Kylie’s health if she remains in Evin prison. And Kylie should never have been imprisoned in the first place. [Foreign minister] Marise Payne should be calling on the Iranian authorities to do the right thing and release Kylie.”

Reports from inside Iran’s prisons say dozens of prisoners have persistent coughs and high fevers, symptoms of coronavirus, but there are no testing kits so no one is being isolated. There are few doctors available to prisoners and little treatment to ease symptoms.

In a report to the Human Rights Council this month, the United Nations’ special rapporteur on the situation of human rights in the Islamic Republic of Iran, Javaid Rehman, said he was seriously concerned about “overcrowding, poor nutrition and a lack of hygiene” in Iran’s jails, and said all political prisoners should be released on humanitarian grounds.

“A number of dual and foreign nationals are at real risk. If they have not ... got [coronavirus] they are really fearful of the conditions,” Rehman said.

At least four political prisoners in Tehran’s Evin Prison, where Moore-Gilbert has been held, have started a hunger strike, led by human rights lawyer Nasrin Sotoudeh. They are demanding “freedom for all political prisoners” in the midst of the Covid-19 outbreak.

Her husband, Reza Khandan, who lives in Tehran with their two children, told the Center for Human Rights in Iran: “Nasrin says, ‘If we’re going to die, let us be by our families’ sides, can’t you let us go even under these circumstances?’”

Iranian officials have not provided any official lists of which prisoners have been released. Nor have they provided any rationale outlining why some have been furloughed while others – including dual and foreign nationals, and political prisoners – remain behind bars.

Iran’s judiciary spokesman Gholam-Hossein Esmaili said 85,000 prisoners had been temporarily released from prison as a precaution against the spread of coronavirus.

“Some 50% of those released are security-related prisoners ... also in the jails we have taken precautionary measures to confront the outbreak,” he said.

Foreign minister Javad Zarif has said Iran’s ability to fight the Covid-19 outbreak was being hampered by US-led sanctions which had crippled the country’s health system.

Speaking on state television, Dr Afruz Eslami cited a study from Tehran’s Sharif University of Technology, presenting three possible scenarios. She said if the Iranian population began to cooperate fully with social distancing now, the country could limit infections to 120,000 and deaths to 12,000.

If isolation measures were only partly followed, 110,000 people might die.

But if people failed to follow the government’s guidance, Iran’s already-strained medical system could collapse, Eslami said. “Medical facilities are not sufficient, there will be four million cases, and 3.5 million people will die,” she said.

Moore-Gilbert, a University of Melbourne professor originally from Bathurst, has been held in Evin prison in Tehran for 18 months, having been sentenced in a secret trial to 10 years in prison for espionage, a charge she denies.

Moore-Gilbert was arrested in September 2018 after having attended an academic conference at which she was invited to speak in Qom. Fellow conference delegates and an interview subject for her academic work flagged her as “suspicious” to the Revolutionary Guards, who arrested her at Tehran airport.

No evidence has ever been presented publicly that Moore-Gilbert was involved in espionage and the Australian government says it rejects her conviction.

The foreign affairs minister, Marise Payne, has said previously “the government has been working extremely hard in relation to the ongoing detention of Kylie Moore-Gilbert”.

The Department of Foreign Affairs and Trade has maintained: “We continue to believe that the best way to secure a successful outcome is through diplomatic channels and not through the media.”